This invention relates to a clamp assembly for a bag sealing machine and, more particularly, to a clamp assembly which is uniquely mounted for cooperation with a sealing drum in developing a stream of plastic bags. This invention is an improvement on my U.S. Pat. No. 4,820,254.
Both this invention and the '254 patent deal with the type of bag making machine described in my U.S. Pat. No. 4,609,367. This utilized clamp assemblies to hold the polyethylene web against the sealing drum during the sealing and cutoff process. Each pair of clamps held the longitudinally folded polyethylene web on the leading and trailing edges of what were to become consecutive segments of the web. A cutoff and sealing wire was moved on a generally radial path that allowed it to pass between the pair of clamps--to create the individual bags. Exemplary of the type of bag made on such machinery was the well-known reclosable bag which employed fastener strips of an interlocking nature.
The prior art machines, and those today, for that matter, generally run two-wide. In such machines, each clamp assembly consists of four clamping surfaces. Prior to the invention of the '254 patent, each clamping surface was allowed to pivot only radially to align itself with the sealing drum surface. Thus, there was no provision for axially aligning the clamp. According to the '254 patent, axial adjustment was achieved by eliminating the rigid securement of the clamps to the pivot shafts and instead providing a radially-extending pivot pin connection therebetween with a slight amount of clearance between the pivot pin on one member and the pin receiving opening on the other member. Although this provided the desired ability for axial adjustment, it did not achieve entirely the desired reduction of set-up time. For example, it took twelve hours to set up the normally 70-80 clamp bar assemblies of the '254 patent while with the instant invention, this has been reduced to less than half the time--often just two to three hours.
According to the invention, this significant advantage has been achieved by (1) adding a channel between the clamp and the pivot shaft, (2) providing a circumferentially-extending (i.e., longitudinally in the sense of web travel with the drum) pivot connection between the arms of the channel and pivot shaft, and (3) providing a clearance between the bight of the channel and the confronting surface of the pivot shaft.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.